Apparatus and method for harvesting a bone-tendon-bone ligament graft

ABSTRACT

A ring blade and drive system, and method of using same, for harvesting bone-tendon-bone ligament grafts having substantially cylindrical bone plugs. The ring blade disclosed is a circular ring having a predetermined arcuate gap formed in its periphery. The drive system includes a blade holder to peripherally hold the ring blade and a fixed-center oscillating mechanism to oscillate the ring blade about its axis within a predetermined arcuate range of motion. The ring blade structure enables the production of a substantially cylindrical bone plug of unlimited length. Harvesting of a bone-tendon-bone ligament graft is facilitated with the ring blade and method disclosed which enables the ring blade to be placed partially around a tendon segment to create bone plugs aligned with the tendon fibers included in the defined tendon segment. The cuts into the bone may be initiated into the bone at either end of the tendon segment from the tendon side through to the exterior of the bone to which the tendon is attached.

This is a divisional application of application Ser. No. 08/412,680,filed Mar. 29, 1995, now U.S. Pat. No. 5,728,118.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to surgical saws. In particular, theinvention relates to a system including a unique drive mechanism and auniquely shaped surgical saw blade adapted to cut a generallycylindrical bone plug. More particularly, the invention relates to asurgical saw and method for harvesting a bone-tendon-bone ligamentgraft.

2. Description of the Prior Art

In certain surgical procedures bone blocks are cut from the bone at theend of a tendon to produce an artificial ligament in the form of abone-tendon-bone graft. For example, for use in cruciate ligamentreconstruction, bone-tendon-bone ligament grafts are often created bycutting a bone block from the patella and tibia and including a portionof the tendon extending between these two bones. Such a graft is theninserted into and secured within prepared bone tunnels in the tibia andfemur in order to simulate the function of anterior or posteriorcruciate ligaments. The bone plugs are generally secured within the bonetunnel by an interference screw which is threaded into the space betweenthe bone plug and the tunnel wall. Since the bone tunnels are generallyprepared by reamers, drills or core drills, the cross-section of thebone tunnels is circular. However, known methods of harvestingbone-tendon-bone ligament grafts produce bone plugs having generallyrectilinear shapes which are then shaped to better fit in the tunnels.The production of a bone-tendon-bone graft generally involves cuttingtwo parallel incisions on each side of the middle third of the patellartendon and then making a three-sided, rectangular cut in the bone ateach end of the tendon. An osteotome is then used to remove the boneblocks. Each bone block must then be trimmed to fit within thecylindrical bone tunnel which is typically on the order of 8-10 mm indiameter. While most known methods for producing bone-tendon-boneligament grafts result in the preparation of bone plugs having agenerally trapezoidal or other rectilinear cross-section, it is oftenpreferred to have bone plugs having a cylindrical cross-section in orderto produce a better fit between the bone plug and the pre-drilled bonetunnel into which the bone plug must fit. It is desirable to have thebone plugs conform to the shape of the bone tunnel as much as possiblein order to promote healing and bony ingrowth of the plug into thetunnel wall.

The preparation of cylindrical bone plugs is known since varioussurgical procedures often require the preparation of cylindrical orsubstantially cylindrical bone plugs. Such bone plugs are generallycreated with the use of devices or instruments commonly referred to astrephines, circular bone saws, core drills, etc. In most of theseapplications, the circular cross-section of the cylindrical bone pluglies perpendicular to the axis of the circular device. Such devices areeither unsuitable or difficult to use in the production ofbone-tendon-bone ligament grafts.

One known device for harvesting the bone of a bone-tendon-bone graft isdisclosed in U.S. Pat. No. 5,320,115 (Kenna). This device incorporates apowered saw having a cylindrical core drill which is oscillated aboutits axis and introduced into the bone at each end of the tendon in adirection toward the tendon. After the bone is cut, the core drill mustbe removed and used to cut the other bone, again toward the tendon. Thecore drill must be tilted as it is advanced in order to produce therelatively cylindrical bone plug and avoid cutting the tendon.

Another saw adapted to produce cylindrical bone plugs is disclosed inU.S. Pat. No. 5,092,875 (McLees). This patent discloses a circular bladehaving a peripheral drive arm extending radially outwardly from the bodyof the blade. The drive arm is oscillated along a semi-circular arc sothat the circular blade oscillates about its axis and is able to cut acontinuous length of cylindrical bone plug. While this device is capableof producing a bone-tendon-bone graft with cylindrical bone plugs, inactual practice this device is difficult to use. Moreover, the methodshown in this patent does not facilitate the production of a partiallycylindrical graft which may be desirable in certain situations.

Because bone plugs are often secured by interference screws insertedinto the space between the plug and the tunnel wall, totally cylindricalbone plugs may not be desirable. Other applications may find totallycylindrical bone plugs desirable, but for many bone-tendon-bone ACLreconstructions the bone plugs should be produced with a flat so a spaceremains between the plug and the tunnel wall into which an interferencescrew will fit. No known prior art devices can easily produce such aplug shape in a bone-tendon-bone graft.

It is accordingly an object of this invention to produce a bone sawsystem for harvesting a bone-tendon-bone graft.

It is also an object of this invention to produce a flat, ring bladecapable of cutting tissue by oscillating about its axis.

It is a further object of this invention to produce a ring blade capableof beginning the cut into a bone at either end of a tendon from thetendon side of the bone.

It is also an object of this invention to produce a bone saw system inwhich the blade may be attached to the drive unit after the blade hasbeen properly positioned adjacent tissue to be cut.

It is an additional object of this invention to produce a ring bladecapable of being easily attached and detached from a drive unit.

It is an object of this invention to produce a bone saw which canproduce a substantially cylindrical bone plug of any desired length.

It is an object of this invention to produce a bone saw which canproduce a substantially cylindrical bone plug having a flat surfacealong one side thereof, the size of this flat surface beingcontrollable.

It is also an object of this invention to produce a ring blade capableof being attached to a drive unit in a selected direction so that thecut may be produced by either a pulling motion or a pushing motion.

It is also an object of this invention to produce a ring blade adaptedto enable the formation of a longitudinally curved surface along aselected point of the bone plug.

It is an additional object of this invention to provide a method ofharvesting a bone-tendon-bone plug through the use of a ring blade.

It is also an object of this invention to produce a bone saw system andmethod for harvesting a bone-tendon-bone graft such that the boneportions of the graft are aligned with the width of the tendon at eachend of the graft.

SUMMARY OF THE INVENTION

These and other objects of this invention are achieved by the preferredembodiment disclosed herein which comprises a cutting blade, generallyreferred to herein as a ring blade, for harvesting a substantiallycylindrical bone plug, the ring blade comprising a substantiallycircular ring having an axis, a periphery with a predetermined arcuategap in the periphery and opposing axially aligned edges. The ring bladehas a cutting means on at least one of the axially aligned edges whichis adapted to make an arcuate cut.

The invention also comprises a surgical system for harvesting abone-tendon-bone graft comprising a ring blade, as described above and ahandpiece for driving the ring blade. The handpiece comprises a powersource, a fixed-center oscillating means and a drive transfer means fortransferring the output of the power source to the fixed-centeroscillating means.

The invention also is an embodiment of the method of harvesting abone-tendon-bone graft from a patellar tendon. The method comprises thesteps of providing a ring blade, as described above, providing a drivemeans for peripherally oscillating the ring blade about its axis, makinga pair of parallel incisions in the patellar tendon and passing the ringblade through the incisions to place it in an orientation with itscutting edge substantially under the tendon. The ring blade is thenattached to the drive means and urged through the bone at a selected endof the patellar tendon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation diagrammatic view in cross-section of asurgical bone saw system constructed in accordance with the principlesof this invention.

FIG. 2 is a cut-away front elevation view of a portion of FIG. 1 showingthe fixed-center oscillating mechanism used in the preferred embodiment.

FIG. 3 shows the fixed-center oscillating mechanism of FIG. 2 at aparticular point in its cycle of operation.

FIG. 4 is a front elevation view of the ring blade used in the systemshown in FIG. 1.

FIG. 5 is a side elevation view of FIG. 4.

FIG. 6 is a front elevation view of a blade holder.

FIG. 7 is an exploded side elevation view showing how the ring blade ofFIG. 4 is assembled with the blade holder of FIG. 6.

FIG. 8 is a front elevation view of the blade holder of FIG. 6 with alatching cover.

FIG. 9 is a side elevation view of the ring blade/blade holder assemblyshowing the latching cover in place.

FIG. 10 is a diagrammatic view of one of the steps of the method ofusing the surgical saw system of FIG. 1.

FIGS. 11, 12, 13 and 14 are diagrammatic views showing other steps inthe method of using the invention on a human knee.

FIGS. 15, 16, 17 and 18 are diagrammatic views showing an alternativemethod of using the invention on a human knee.

FIG. 19 is a diagrammatic view showing another step in the method ofusing the invention.

FIGS. 20a and 20b are diagrammatic views of the surface of a bone plugproduced by the surgical saw system of FIG. 1.

FIGS. 21a and 21b show a front elevation and side elevation view,respectively, of an alternate embodiment of a blade suitable for usewith the invention.

FIGS. 22a and 22b show a front elevation and side elevation view,respectively, of an alternate embodiment of a blade suitable fur usewith the invention.

FIGS. 23a and 23b show front elevation and side elevation views,respectively, of an alternate embodiment of a blade suitable for usewith the invention.

FIGS. 24a and 24b show front elevation and sectional elevation (alongthe line 24b--24b) views, respectively, of an alternate embodiment of ablade suitable for use with the invention.

FIGS. 25a and 25b show a front elevation and sectional elevation (alongthe line 25b--25b) views, respectively, of an alternate embodiment of ablade constructed in accordance with the principles of this invention.

FIGS. 26a and 26b show front elevation and side elevation (along theline 26b--26b) views, respectively, of an alternate embodiment of ablade constructed in accordance with the principles of this invention.

FIG. 27 is a front elevation view of a blade holder for use with theblade of FIGS. 26a and 26b.

FIG. 28 is a side elevation view in cross-section of the blade holder ofFIG. 27 (with a cover in open position) and the blade of FIGS. 26a and26b.

FIG. 29 is a front elevation view of the blade holder of FIG. 27assembled with the blade of FIGS. 26a and 26b.

FIG. 30 is a side elevation view in cross-section of FIG. 29 showing acover in place.

FIG. 31 is a front elevation view of FIG. 30.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, surgical saw system 10 comprises a handpiece 12having a handle 14, a motor 16 and a drive mechanism 18 for driving aring blade 20. In the preferred embodiment, handpiece 12 is part of abattery operated system which further comprises a battery pack 22 and iscontrolled by a motor control circuit 24 and activated by a trigger 26in a conventional manner. As will be understood, the function of system10 is to produce a fixed-center oscillating motion of ring blade 20 sothat a bone-tendon-bone graft may be easily produced with substantiallycylindrical bone plugs at each end of a connecting tendon.

Drive mechanism 18 comprises those components necessary to convert therotary motion of the drive shaft of motor 16 into a fixed-centeroscillating motion of blade 20. The term "fixed-center" is used to referto the fact that ring blade 20 can cut through a surface merely byoscillating around its axis 28 within a plane perpendicular to the axis,i.e. its center is fixed since no translational motion of the axis isrequired to produce this oscillation. Since those skilled in the artwill understand the operation of drive mechanism 18 without a detailedexplanation of each of the components (i.e. bearings, etc.), only themain components will be described. In the preferred embodiment, drivemechanism 18 comprises a bevel gear 30 secured to the drive shaft ofmotor 16 and another bevel gear 32 operatively connected to bevel gear30 in order to transfer the rotary motion to a first horizontal driveshaft 34 on which is mounted an eccentric gear 36. Eccentric gear 36 isjoined by a connecting rod 38 to a crank assembly 40 which is in turnconnected to a second horizontal drive shaft 50. The function ofcomponents 30 to 40 is to convert the rotary motion of motor 16 to anoscillating motion of drive shaft 50 which, in the preferred embodiment,oscillates about its axis 52 within a range of ±12°. It will beunderstood by those skilled in the art that, while drive mechanism 18 isconstructed as described in order to operate within handpiece 12 whichhas been ergonomic-ally designed for the particular application ofharvesting bone-tendon-bone grafts from a human knee, numerous otherembodiments could be devised for producing the oscillatory motion ofdrive shaft 50.

The oscillating output of drive mechanism 18 is the input tofixed-center oscillating subassembly 60 which converts the oscillatorymotion of drive shaft 50 into the fixed-center oscillating motion ofblade 20. Referring to FIGS. 2 through 4, it will be noted thatsubassembly 60 comprises a blade holder or frame 62, a first bracket 64and a second bracket 66. The first and second brackets are aligned in acommon first plane P1 with a portion of blade holder 62. As describedbelow in FIGS. 6 through 9, ring blade 20 is held securely within bladeholder 62 so as to be aligned within a plane P2 parallel to plane P1.Connecting rods 68 and 70 pivotably join blade holder 62 and first andsecond brackets 64, 66. Each connecting rod 68 and 70 has a distal end72 and 74, respectively, and a proximal end 76 and 78, respectively.Blade holder 62 is pivotably joined to distal end 72 at pivotingjunction 80 and to distal end 74 at pivoting junction 82. The proximalends 76 and 78 of the connecting rods are similarly pivotably joined tosecond bracket 66 at pivoting junctions 84 and 86, respectively. Firstbracket 64 is similarly pivotably joined to the connecting rods at apoint along their lengths between second bracket 66 and blade holder 62at pivotable junctions 88 and 90. The second bracket 66 is pivotablymounted on pivot point 92 and first bracket 64 is pivotably mounted onan idling pivot point 94, and the pivot points are fixedly mountedrelative to housing 12. Pivot point 92 is also aligned with axis 52 andfixedly connected to drive shaft 50 so that the oscillatory motion ofdrive shaft 50 is converted into the oscillatory motion of secondbracket 66. Pivot point 94 is essentially the axis of a support shaft 96(best seen in FIG. 1) which is parallel to drive shaft 50. It will beunderstood that the various pivots and pivotable junctions include allthe necessary bearings, sleeves, pins, etc. which may be required toperform the described function.

The lengths of the connecting rod sections between the pivot pointsproduce a symmetrical structure about a line joining ring blade axis 28with pivot points 92 and 94. Thus, length L1 between pivotable junctions84 and 88 is equal to length L2 between pivotable junctions 86 and 90.Also, length L3 between pivotable junctions 80 and 88 is equal to thelength L4 between pivotable junctions 82 and 90. As shown in FIG. 3, assecond bracket 66 oscillates about its pivot point 92, first bracket 64and blade holder 62 must necessarily follow with a similar oscillatorymotion. The lengths L1, L2 need not equal the lengths L3, L4 to producethis motion.

The proximal ends of the connecting rods may be joined to any mechanismwhich can produce the desired motion of the ring blade. If a structuresuch as that shown in FIGS. 2 and 3 is used, the spatial relationshipbetween the central pivot and the two pivotable junctions on one bracketis the same as that on the other bracket. That is, these points lie in acommon plane at the vertices of a triangle on each bracket. Thisspatial, triangular relationship is the same as that between the axis 28of the ring blade and the pivotable junctions on the blade holder. Ifsuitably strong materials are used and if the connecting rods arerestricted to maintain their vertical alignment as they reciprocate inresponse to the oscillatory motion of bracket 66, it may be possible toachieve the same operation with only one bracket.

It has been found that in order to achieve certain advantages of ringblades the ring may be formed with a predetermined annular gap which, aswill be understood below, facilitates the use of the blade in thecreation of bone-tendon-bone grafts. This annular gap results in theshape of the ring being substantially C-shaped rather than totallyenclosed. However, it will be understood that the term "ring blade" asused herein is intended to mean all blades having circular peripheriesincluding totally enclosed circular rings and C-shaped rings, unlessotherwise specified.

As shown in FIGS. 4 and 5, ring blade 20 has a substantially circularbody 100 having a periphery which has two ends 102 and 104, these endsdefining an arcuate gap 106 therebetween. Body 100 encloses a circularopen area 115 around axis 28. Each end 102 and 104 is attached tooutwardly extending support portions comprising members 108 and 110,respectively, and the distal ends of these support members are bentoutwardly into flanges 112 and 114, respectively. In the preferredembodiment, the body, support members and flanges are formed from asingle flat piece of suitable material (e.g. steel, plastic, etc.) andaligned with axis 28 as best seen in FIG. 4. In an alternate embodimentbest seen below in FIGS. 26a and 26b, the ends 102 and 104 are attachedto or integrally formed with mounting blocks which provide a means tosecure the ring blade to a blade holder and also serve as bearings forpivoting junctions 80 and 82. The size of the arcuate gap 106 and thedistance between support members 108 and 110 is variable and a matter ofchoice depending upon the ultimate application for which the ring blade20 is designed. Indeed, as will be noted below, alternate embodiments ofa ring blade may be totally enclosed. Body 100 has a pair of oppositelyfacing, axially aligned front and back edges 120 and 122, respectively.As best seen in FIG. 5, body 100 is tapered so that its distal tip 124is narrower than the remainder of the body. For ease of description theterm "length" may be used to refer to those distances parallel to axis28 and the term "width" may be used to refer to distances perpendicularto axis 28. Thus, the length of ring blade 20 at point 124 is shorterthan its length adjacent support members 108 and 110. The curvature ofback edge 122 facilitates the tilting of the ring blade in order toproduce a curve in the cylindrical bone plug, as will be understoodbelow. Front edge 120 is provided with a cutting means such as aplurality of cutting teeth 126 along that portion of the edge which iscircular. The ring blade is capable of being used with its front,cutting edge pointed either toward or away from a user. Other cuttingsurfaces could equally be utilized so long as they could be adapted tocut the tissue with the slight oscillatory motion of ring blade 20. Itwill be understood that portions of the ring blade could be providedwith different cutting surfaces depending upon the tissue to be cut. Forexample, smooth tissue would be more likely to be cut by a knife edgerather than a plurality of teeth. Furthermore, different cutting edgescould be provided on different portions of the blade depending upon theparticular application for which the system is to be used. One possibleembodiment could include a bone cutting edge on either side of distaltip 124 with a soft tissue cutting edge adjacent each end of the bonecutting portion. Another ring blade embodiment could utilize a cuttingedge on both front and back edges 120 and 122. If desired, the cuttingedge on front edge 120 could be different from the one on the back edge.

The manner in which ring blade 20 is held within hand-piece 12 is bestunderstood by reference to FIGS. 6 through 9. Blade holder 62 is bestseen schematically in FIG. 6 with various associated components removed.The blade holder is intended to hold the blade peripherally, from apoint spaced from axis 28 to enable a peripherally oscillating drivemeans to produce a fixed-center oscillating motion. The termperipherally oscillating means any type of drive means that acts from apoint outside the circular periphery of the ring blade. Blade holder 62comprises a generally rectilinear body 130 having a pair of uniquelyshaped, spaced slots or recesses 132 and 134 adapted to receivecorresponding support members and flanges 108, 112 and 110, 114,respectively. The slot in blade holder 62 may be adapted to hold othershapes of support members and even totally circular blades (shown belowin FIGS. 21 through 25). Additionally, blade holder 62 may be adapted tohold a modified ring blade having each of its ends encased within aplastic or other material having a chosen shape to fit intocorresponding recesses in the blade holder. It will be noted that thesymmetry of the holding device enables ring blade 20 to be placed in oneof two positions, 180° apart, so the cutting edge 126 could face ineither of two different directions. The body 130 of blade holder 62 hasa locking device in the form of a cover 140 hingedly joined to a raisedboss 142. A spring-loaded latch pin or ball 144 extends from the frontof blade holder 62 to be received within a hole or detent 146 within thecover 140 when the latter is closed to hold ring blade 20 within slots132 and 134.

A depth penetration gauge 150 is attached to the front of blade holder62 and has a distal tip 152 which extends toward axis 28 of ring blade20 as best seen in FIG. 9. The size of depth gauge 150 may be chosen tocontrol the penetration of the blade into bone to produce a desirablesize of bone plug. The depth gauge also serves as an anti-dive mechanismto minimize any tendency of ring blade 20 to cut too deeply into thebone. Such deep cuts could, if permitted to occur, cause wedging of theblade and excessive friction. The depth gauge 150 thus facilitatesproper operation of the invention. It operates best when situated on theside of blade holder 62 adjacent the cutting edge 126 and spaced fromthe cutting edge by some distance which, in the preferred embodiment, ison the order of 0.125 inches.

A method of using the system 10 is shown in FIGS. 10 through 18. FIG. 10shows one environment in which system 10 may be used as being a kneejoint having a femur 200, a tibia 202, a patella 204 and a patellartendon 206. In harvesting a bone-tendon-bone ligament graft from thepatellar tendon 206, a portion of the patellar bone 204 is excised alongwith a portion of tibial bone 202 and the interconnecting portion 212 ofpatellar tendon 206. One method of forming the patellar tendon portionor segment 212 of the graft is to form a pair of parallel incisions 208and 210 between the bone at the patella side of the tendon and the boneat the tibia side of the tendon. This portion is generally the centralthird of the patellar tendon ligament. Ring blade 20 may then be"wrapped" or placed partially around tendon portion 212 by passing theportion through annular gap 106 in order to place the cutting edge 126substantially under tendon portion 212. Flanges 112 and 114 may then besecured within blade holder 62 in the manner shown in FIGS. 6 through 9in order to continue the procedure. One advantage provided by theinvention is that the longitudinally extending fibers of tibial portion212 are assured to be aligned with the bone plug to which these fibersare attached because each bone plug is formed from the tendon side andout through the bone.

As shown in FIGS. 11 through 14, handpiece 12 with attached ring blade20 may be used in a pulling fashion to cut both the tibial and patellarbone plugs from a human knee 214. In this procedure, the cutting edge ofring blade 20 is arranged to face toward the body of handpiece 12, andtherefore toward the user so that a cutting action occurs on pulling thehandpiece 12 toward the user in the direction of arrow 216. As shown inFIG. 11, the initial cutting action into the patellar bone producesstraight annular cut 220 (best seen in FIG. 19) which is then smoothlyjoined to a curved annular cut 224 as handpiece 12 is tipped in thedirection of arrow 225 as shown in FIG. 12 to cause blade 20 to exit thebone. Similarly, after the blade is disconnected from the handpiece andrepositioned as shown in FIG. 13, the first cut into the tibia producesa straight cut 230 which is then curved at 232 as the handpiece istilted to cause blade 20 to exit the bone.

If desired, ring blade 20 may be reversed to have the cutting edgefacing away from the body of the handpiece as shown in FIGS. 15 through18 so that both patellar and tibial bone plug sections could produced bya pushing action. In all other respects, the procedure shown in FIGS. 15through 18 is similar to that shown in FIGS. 13 through 16. The surgicalinstrument shown in FIG. 1 is the one that is depicted in FIGS. 15through 18 in the sense that it shows ring blade 20 facing away from auser holding handpiece 12. While the specific manner in which the blademay be repositioned 180° to face toward the user is not shown, thoseskilled in the art will understand how this may be accomplished.

As diagrammatically shown in FIG. 19, ring blade 20 may be passedthrough patellar bone 204 in direction 216 (as also shown in FIG. 11) tocreate an annular cut 220 formed by the oscillating cutting edge of ringblade 20. The curved back edge 122 enables the handpiece (not shown) andblade 20 to be tilted, as shown by arrow 222, in order to guide thedistal tip 124 of the ring blade in an arcuate manner to curve annularcut 220 upwardly to create a rounded end 224 in the patellar bone plug226. For simplicity, the blade is shown only in one position but it willbe understood that the annular cut 220 is formed as the blade movesthrough the bone. A similar procedure may be used to round the tibialbone plug (not shown).

The resulting bone plug 226 is also shown in FIGS. 20a and 20b withoutthe associated patellar tendon. The bone plug has a flat top surface 240created because of depth gauge 150 and a cylindrical body surface 242because of blade body 100. The texture of the cylindrical body surfacemay be varied by producing the cutting means at the front edge of ringblade 20 to create a desired cutting effect. For example, if teeth 126are provided as shown in FIG. 4, the teeth may be set inwardly andoutwardly relative to axis 28 (as best seen in FIG. 19) so that, uponoscillation of ring blade 20, a serrated pattern of grooves 244 will beformed in the surface of bone plug 226. Such serrations may enhancefrictional engagement between the bone plug and its bone tunnel and mayalso assist in healing bony ingrowth. The teeth could be set in only onedirection if desired (e.g. radially inwardly).

In addition to the preferred embodiment of the ring blade describedabove, the invention is easily adaptable to other blade configurations.For example, a modified ring blade holder 262 may be provided to serveas a peripheral attachment device to retain a totally circular ringblade 264 as shown in FIGS. 21a and 21b and 24a and 24b. The blade couldbe a fixed portion of the holder or it could be detachable therefrom. Asimilar blade holder 272 could be provided to hold an axially extendedcircular blade 274 as shown in FIGS. 22a and 22b. While this is similarto a prior art core drill, this embodiment enables the formation of acontinuous length of cylindrical bone plug. Blade 274 could have a closeback end surface 276 with an axial bore 278 to facilitate pushing a coreout of the blade. Another possible configuration is blade holder 282adapted to hold a flat oscillating blade 284 as shown in FIGS. 23a and23b. Thus, it will be understood by those skilled in the art that avariety of blade styles could be produced to be used by a handpiececonstructed in accordance with the principles of this invention.

Variations in the teeth formed on the blades adapted for use with thesystem are also feasible, both on totally circular ring blades and onC-shaped ring blades. For example, as shown in FIGS. 24a and 24b, acircular blade 264a could have a smooth arcuate shank portion 265adapted for enabling blade 264a to be clamped to an appropriatelymodified blade holder and the remaining portion of the annular body ofblade 264a could be provided with axially facing teeth 266 and radiallyfacing teeth 267. Such an arrangement would enable the blade to cutdirectly into the bone at one end of the patellar or tibial bone plug,in a plane perpendicular to the bone surface, and then be movedlongitudinally along the bone plug to and through the tendon toward andthrough the other bone plug.

An alternative embodiment of ring blade 264b is shown in FIGS. 25a and25b having a plurality of axially facing teeth 296 arrayed around theentire periphery of one edge of the blade. Such an arrangement wouldenable the body 298 behind the teeth to be smooth enough to be easilyengageable by an appropriate clamping mechanism to hold it to a suitableblade holder.

The method of harvesting a bone-tendon-bone graft with a totallycircular blade may be similar to any one of the methods described aboveexcept that the blade would need to first begin forming the graft fromone end in the bone. The ring or circular blade could then be advancedthrough the bone to produce one bone plug, along the already cut tendonand through the bone at the other end to produce the other bone plug.Alternatively, the blade could be advanced through the bone on one sideof the tendon and then retracted when the cut is completed. The bladecould then be advanced through the bone at the other end and retractedonce that cut is completed.

Another alternative embodiment of the invention is shown in FIGS. 26aand 26b as ring blade 300 having a circular body 302 with ends 304 and306 encased in injection molded block members 308 and 310, respectively.Block members 308 and 310 are molded around ends 312 and 314,respectively, and include cylindrical bores 316 and 318, respectively.Bores 316 and 318 provide simple bearings for coupling ring blade 300 toa complementarily shaped blade holder 320. As best seen in FIGS. 27 and28, blade holder 320 is attached to the distal ends of connecting rods68 and 70 (similarly to blade holder 62 shown in FIG. 2) and comprises abody 322, receiving recesses 324 and 326, and transversely fixed,polished pivot pins 328 and 330 secured to the connecting rods 68 and70, respectively. The body 322 is retained adjacent the connecting rodsby pin shoulders 332 and 334. When blade holder 320 and ring blade 300are assembled, the proximal ends of pivot pins 328 and 330 fit intorecesses 324 and 326, respectively, as best seen in FIGS. 29 and 30.Block members 308 and 310 may be formed from any suitable materialcapable of rigidly holding the body 302 and capable of forming recessesto serve as bearing surfaces about pivot pins 328 and 330. These bearingsurfaces are replaced with each new ring blade as the old one isdisposed of. Blade holder 320 is provided with a hinged locking cover340 which is omitted for clarity in FIGS. 27 and 29, and is shown openin FIG. 28 and closed in FIGS. 30 and 31. Spring loaded ball or pin 342on body 320 seats within recess 344 in cover 340 to hold the cover inplace.

It will be understood that the bearing structure used in ring blade 300is easily adaptable to the blades and corresponding blade holders shownin FIGS. 21 through 25.

It will be understood by those skilled in the art that numerousimprovements and modifications may be made to the preferred embodimentof the invention disclosed herein without departing from the spirit andscope thereof.

What is claimed is:
 1. A method of harvesting a bone-tendon-bone graftfrom a patellar tendon comprising the steps of:making a pair of parallelincisions in the patellar tendon to define a tendon segment; providing aring blade having a predetermined annular gap in its periphery and atleast one axially aligned cutting edge; providing a drive means forperipherally oscillating said ring blade about its axis; passing saidring blade through said incisions to place it in an orientation withsaid cutting edge substantially under said tendon segment and thenproceeding the attaching said ring blade to said drive means;peripherally oscillating said ring blade about its axis; and urging saidring blade through the bone at a selected end of said patellar tendon.2. A method according to claim 1 further comprising the step of:tiltingsaid ring blade relative to said bone at a predetermined point in itspassage through the bone to produce a rounded bone plug end as said ringblade exits the bone.
 3. A method according to claim 1 furthercomprising the steps of:disengaging said ring blade from said drivemeans; disengaging said ring blade from said tendon segment; placingsaid ring blade around said tendon segment with said cutting edge facingthe bone at the other, attached end of said tendon segment; urging saidring blade through the bone at said other end.
 4. A method of harvestinga bone-tendon-bone graft from a patellar tendon comprising the stepsof:providing a ring blade having at least one bone cutting edge and atleast one soft tissue cutting edge facing in the same axial direction assaid bone cutting edge; providing a drive means for peripherallyoscillating said ring blade about its axis; attaching said ring blade tosaid drive means; urging said ring blade into the bone from a selectedend of the patellar tendon, through the tendon and through the bone atthe other end of the tendon.
 5. A method according to claim 4 whereinsaid bone cutting edge subtends a first predetermined arcuate distancealong one edge of said ring blade and wherein said soft tissue cuttingedge subtends second and third predetermined arcuate distances, one oneach end of said bone cutting edge.